THE INFLUENCE OF NEW D-SECO-ESTRONE DERIVATIVES ON THE BEHAVIOR OF THE CHOLESTERIC LIQUID CRYSTALS BINARY MIXTURES

2006 ◽  
Vol 20 (21) ◽  
pp. 2999-3013 ◽  
Author(s):  
D. Ž. OBADOVIĆ ◽  
M. STOJANOVI ◽  
S. JOVANOVIĆ-ŠANTA ◽  
D. LAZAR ◽  
A. VAJDA ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Binary Mixtures ◽  
Average Distance ◽  
Molecular Mechanic ◽  
Molecular Structures ◽  
X Ray Diffraction ◽  
Cholesteric Liquid Crystals ◽  
Cholesteric Phase ◽  
Molecular Length

We have studied the influence of the new chiral non-mesogenic seco-estrone derivatives 1-7, synthesized in several synthetic steps starting from estrone, onto the physical characteristics of the binary mixtures of cholesteric liquid crystals. We have examined the phase transitions of the mixture of cholesteryl laurate and cholesteryl enantate with the added chiral non-mesogenic additives 1-7 (45%-45%-10%; Mix.1-Mix.7, respectively). A considerable shift of the I → Ch phase transition temperature, as well as of the temperature of the SmA * phase formation, was observed. X-ray diffraction data enabled the determination of the molecular structures of the compounds 3, 5, 6 and 7, the crystal lattice parameters of the new chiral additives and their molecular length (ℓ) and width (d*), as well as some parameters of the mixtures Mix.1-Mix.6: the thickness of smectic layers and the longitudinal spacing distance in the cholesteric phase (d) and the average distance between the long axes of neighbouring molecules (D). Using molecular-mechanic calculations, on the basis of solved molecular structures, the most probably conformation of the other compounds (1, 2 and 4) used in this work is determined. We have also investigated the influence of these chiral additives onto the pitch of the cholesteric helix of a binary mixture of cholesteric liquid crystals.

Notizen: Bestimmung des Helixdrehsinnes cholesterischer Phasen mit der Grandjean-Cano-Methode / Determination of the Helical Sense of Cholesteric Liquid Crystals Using the Grandjean-Cano Method

1977 ◽  
Vol 32 (8) ◽  
pp. 899-902 ◽  
Author(s):  
G. Heppke ◽  
F. Oestreicher
Keyword(s):  
Molecular Structure ◽  
Liquid Crystals ◽  
Nematic Phase ◽  
Ring System ◽  
Cholesteric Liquid Crystals ◽  
Cholesteric Phase ◽  
Chiral Compounds ◽  
Helix Pitch

Abstract A simple way of determining the helix screw sense of a cholesteric phase using the Grandjean-Cano method is described. The helix pitch as well as its sense is investigated for ten cholesteric phases, induced by mesogenic chiral com­pounds in the nematic isomere mixture of 4-methoxy-4′-n-butylazoxybenzene (Nematic Phase 4, Merck). For the chiral compounds with nematic-like molecular structure it is found that the screw sense alternates with the number of bonds between the chiral centre and the ring system.

Crystal structure determination of the conformation of two bicyclo[3.3.1]nonan-ones

1985 ◽  
Vol 63 (6) ◽  
pp. 1166-1169 ◽  
Author(s):  
John F. Richardson ◽  
Ted S. Sorensen
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Chair Conformation ◽  
Molecular Structures ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Final Agreement

The molecular structures of exo-7-methylbicyclo[3.3.1]nonan-3-one, 3, and the endo-7-methyl isomer, 4, have been determined using X-ray-diffraction techniques. Compound 3 crystallizes in the space group [Formula: see text] with a = 15.115(1), c = 7.677(2) Å, and Z = 8 while 4 crystallizes in the space group P21 with a = 6.446(1), b = 7.831(1), c = 8.414(2) Å, β = 94.42(2)°, and Z = 2. The structures were solved by direct methods and refined to final agreement factors of R = 0.041 and R = 0.034 for 3 and 4 respectively. Compound 3 exists in a chair–chair conformation and there is no significant flattening of the chair rings. However, in 4, the non-ketone ring is forced into a boat conformation. These results are significant in interpreting what conformations may be present in the related sp2-hybridized carbocations.

The Influence of New Chiral Additives on Phase Transitions of Binary Mixtures of Some Cholesteric Liquid Crystals

2000 ◽  
Vol 321-324 ◽  
pp. 1113-1118 ◽  
Author(s):  
D.Ž. Obadović ◽  
A. Vajda ◽  
S. Jovanović-Šanta ◽  
M. Stančić ◽  
J. Petrović
Keyword(s):  
Phase Transitions ◽  
Liquid Crystals ◽  
Binary Mixtures ◽  
Cholesteric Liquid Crystals

scholarly journals Statistical Theory of Elastic Constants of Cholesteric Liquid Crystals

2002 ◽  
Vol 57 (3-4) ◽  
pp. 105-118 ◽  
Author(s):  
Andrzej Kapanowski
Keyword(s):  
Statistical Theory ◽  
Liquid Crystals ◽  
Elastic Constants ◽  
Binary Systems ◽  
Cholesteric Liquid Crystals ◽  
Cholesteric Phase ◽  
Small Density ◽  
Nematic Phases ◽  
The Stability ◽  
The One

A statistical theory of cholesteric liquid crystals composed of short rigid biaxial molecules is presented. It is derived in the thermodynamic limit at a small density and a small twist. The uniaxial (biaxial) cholesteric phase is regarded as a distorted form of the uniaxial (biaxial) nematic phase. The chirality of the interactions and the implementation of the inversion to the rotation matrix elements are discussed in detail. General microscopic expressions for the elastic constants are derived. The expressions involve the one-particle distribution function and the potential energy of two-body short-range interactions. It is shown that the elastic constants determine the twist of the phase. The stability condition for the cholesteric and nematic phases is presented. The theory is used to study unary and binary systems. The temperature and concentration dependence of the order parameters, the elastic constants and the twist of the phase are obtained. The possibility of phase separation is not investigated.

scholarly journals LCDiXRay: a user-friendly program for powder diffraction indexing of columnar liquid crystals

2014 ◽  
Vol 47 (2) ◽  
pp. 668-679 ◽  
Author(s):  
Nicolas Godbert ◽  
Alessandra Crispini ◽  
Mauro Ghedini ◽  
Manuela Carini ◽  
Francesco Chiaravalloti ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Structural Information ◽  
Structural Parameters ◽  
X Ray Diffraction ◽  
Cell Parameters ◽  
Cross Section Area ◽  
Section Area ◽  
Columnar Mesophases ◽  
User Friendly

The formulation of a standard computerized procedure for the indexing of powder X-ray diffraction (PXRD) patterns of columnar liquid crystals, with the determination of all structural information extracted from a properly indexed PXRD spectrum and the attribution of the columnar mesophase symmetry, is presented. In particular, the proposed program notably accelerates the identification of columnar mesophases together with thein situdetermination of their structural parameters such as mesophase type, space group, cell parameters, cross-section area, intermolecular stacking distance between consecutive discoids and, in the case of ordered mesophases, the estimation of the number of molecules constituting each discoid.

Automated determination of n-cyanobiphenyl and n-cyanobiphenyl binary mixtures elastic constants in the nematic phase from molecular simulation

2020 ◽  
Vol 5 (6) ◽  
pp. 1131-1136
Author(s):  
Jiale Shi ◽  
Hythem Sidky ◽  
Jonathan K. Whitmer
Keyword(s):  
Liquid Crystals ◽  
Molecular Simulation ◽  
Elastic Properties ◽  
Binary Mixtures ◽  
Elastic Constants ◽  
Nematic Phase ◽  
New Techniques ◽  
New Applications ◽  
Automated Determination

This work explores new techniques in molecular simulation which can be used to precisely determine and engineer elastic properties of liquid crystals for new applications.

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